<h3>1.描述</h3>
<p>树组件通过接口配置class类名设置图标(供于内部测试、追溯，不对外暴露该实例)</p>
<h3>2.示例</h3>
<div style="width: 500px">
  <ti-tree [data]="data" [multiple]="true" id="tree-icon"> </ti-tree>
</div>
